The present invention relates to a data processing device with a pixel image memory which is suitable for use with an office or personal computer or a work processor each having a bit map display connected thereto or a laser beam printer or like image printer. More particularly, the present invention relates to a data processing device which allows various kinds of rules to be written in a pixel image memory rapidly and easily, thereby enhancing system processing performance.
A data processing device associated with a bit map display or an image printer, for example, usually includes a pixel image memory for processing data on a pixel basis. Written into the pixel image memory are graphs and other diagrams, characters, etc. The pixel image memory is addressed in terms of a word or a byte and, therefore, data need be written into the memory or read thereoutof on a word or byte basis. Such a processing system is more time-consuming than one which uses character codes. Concerning vertical and horizontal rules which often need be drawn, a prior art data processing device has customarily written line data in a pixel image memory by means of firmware. Even the prior art device uses a method which features a high-speed processing capability, so long as relatively simple lines such as solid lines are desired.
However, when it is desired to selectively draw many kinds of rules such as thin and thick solid lines, thin and thick dotted lines, thin and thick broken lines and thin and thick dash-and-dot lines as is often experienced with modern word processors and other data processing devices, the method in accordance with the prior art data processing device cannot be implemented without complicating the program and, moreover, without allocating a substantial period of time to processing for executing the program. Such undesirably lowers the processing performance of the system.
Specifically, it is preferably that such a pattern as a dotted line or a dash-and-dot line be positioned symmetrically in the lateral direction within a one-character write area in order to enhance attractive appearance, while the symmetrical position is unattainable unless an operation for shifting rule data is provided. To process data associated with various kinds of lines by use of the prior art device, an intricate control is required which would lower the system processing performance.